1. Field of the Invention
The present invention relates to a pressure sensor.
2. Description of the Related Art
A pressure sensor using a capacitive pressure transducer is known as disclosed, for example, in U.S. Pat. No. 4,875,135. The pressure sensor of this type is employed, for example, in a cooler for automobiles.
The pressure sensor of the above-described U.S. Patent has, as shown in FIGS. 1A and 1B, a metal main housing member 10 screwed at its one end with a refrigerant pipe in the cooler to communicate with refrigerant in the refrigerant pipe, and a non-electrically conductive material connector housing member 12 coupled to the other end portion of the main housing member 10 by bending the distal end of the other end portion to engage with the connector housing member 12.
The main housing member 10 has a coupling portion 10a having a communication hole on the inner periphery of which female threads are formed, and a trough-shaped portion 10b fixed at its bottom wall to one end of the coupling portion 10a. At the bottom wall of the trough-shaped portion 10b, a punched portion punched toward the communication hole of the coupling portion 10a is formed. The side surfaces of the punched portion are sheared off from the bottom wall of the trough-shaped portion 10b to communicate the communication hole with the inner space of the trough-shaped portion 10b. A capacitive pressure transducer 16 placed on the bottom wall of the trough-shaped portion 10b through an annular sealing ring 14 is disposed in the inner space of the trough-shaped portion 10b, and the capacitive pressure transducer 16 is pressed on the sealing ring 14 by the inner end of the connector housing member 12 coupled to the main housing member 10.
The connector housing member 12 has a cylindrical shape the outer end of which is closed by a partition wall 12a from an outer space, and the base ends of a plurality of connector terminals 18 are fixed to the partition wall 12a so that they extend in a longitudinal direction of the connector housing member 12. At the partition wall 12a of the connector housing member 12, a cylindrical terminal protection cover 12b extending in the longitudinal direction is formed to surround the plurality of connector terminals 18 and to protect the plurality of connector terminals 18 against an external force and an outer environment.
A sealing space 20 is constructed by a region between the partition wall 12a and the capacitive pressure transducer 16 in the inner space of the connector housing 12, and a flexible board 22 is contained in the sealing space 20 in a folded state. Various electronic parts 22a for constructing a predetermined electric circuit are mounted on one surface of the flexible board 22, and they are located inside of the folded flexible board 22. The upper half portion of the flexible board 22 is structurally and electrically fixed to the base end portions of the plurality of connector terminals 18, and the lower half portion of the flexible board 22 is structurally and electrically fixed to a plurality of terminals (not shown) on the upper surface of the capacitive pressure transducer 16.
The above-described pressure sensor has a calibration opening 24 at the peripheral wall of the mainhousing side end portion of the connector housing 12. The calibration opening 24 communicates the sealing space 20 with the outer space to be used to calibrate the predetermined electric circuit on the flexible board 22 for the capacitive pressure transducer 16 from the outer space side in the final step of a production line of the pressure sensor. The calibration opening 24 is sealed, after the calibration work is finished, by a viscous rubber-like sealing material 26.